Revealing the formation mechanism of in-situ Y-rich belt in gradient NiCoCrAlY coating

To investigate the formation mechanism of in-situ Y-rich belt in a gradient NiCoCrAlY coating, the chemical composition and microstructure of NiCoCrAlY + AlNiY coating at various stages of vacuum annealing were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicated that the Y-rich belt formed due to the sweeping effect of the inward-moving Al-rich layer interface during annealing. Additionally, the Y-rich belt consisted of numerous fine Y 2 O 3 precipitates. • The Y-rich belt within a gradient NiCoCrAlY coating is investigated. • The inward-moving Al-rich layer interface leads to the formation of Y-rich belt. • The Y-rich belt consists of numerous fine Y 2 O 3 precipitates.